Pneumatic rendering machine



Jan. 12, 1960 J. R. HARRIS 2,920,943

PNEUMATIC RENDERING MACHINE Filed April 21, 1958 3 Sheets-Sheet 1 FIG.1

INVENTOR.

A f/orngy Jan. 12, 1960 J. R. HARRIS PNEUMATIC RENDERING MACHINE 3Sheets-Sheet 2 Filed April 21, 1958 INVENTOR. John R H0 H5 BY WM W Afforney V 0: W. m 0:

Jan. 12, 1960 J. R. HARRIS PNEUMATIC RENDERING MACHINE Filed April 21,1958 3 Sheets-Sheet 3 INVENTOR. John R Harr '5 BY 716,45 74 W A f/orneyQ: 8 0Q: 0 Q \ww mw OK mu PNEUMATIC RENDERING MACHINE John R. Harris,Atlanta, Ga., assignor to Bullock Manufacturing Company, Inc., acorporation of Georgia Application April 21, 1958, Serial No. 729,573

8 Claims. (Cl. 23-269) This invention relates to pneumatic renderingmachines and more particularly to rendering machines wherein material tobe rendered is subjected to the rendering action of a flow of hot airwhile simultaneously being agitated mechanically.

In machines of this type it has been the practice to apply heat byapplying steam to the material to be rendered or to enclose the materialin a container to which heat is applied externally, the solid materialbeing separated from the rendered liquid by wayof a perforated strainer.In some instances the air is heated by'being passed over or through:some sort of heat exchanger. Most such machines are inefficient due topoor utilization of heat or else produce a solid residue which issaturated with grease or may allow bits of solid material to accumulatein the rendered liquid.

A principal object of this invention is to provide a rendering machineof greatly improved efficiency especially insofar as heat utilization isconcerned.

Another object of my invention is the provision of a safegas firedpneumatic rendering machine.

Still another object of my invention is to avoid subjecting the renderedliquid and the solid residue to any unnecessary heating while at thesame time performing a thorough rendering operationthereby to improvethe quality of the products produced by a rendering operation. I

A further object of this invention is the provision of an improvedrenderingmachine which is easy and simple to ing cavity for collectingthe rendered liquid. Accord- .ingto a feature of the invention theoutlet passage slants upwardly and communicates with the interior of themachine at a point between the rendering cavity and the United StatesPatent is an end view of the right hand end of the machine as viewed inFig. 1; Fig. 3 is a cross sectional view taken along the line 3-3 asindicated in Fig. 1; Fig. 4 is an end view of the machine taken from theleft hand end thereofas viewed in Fig. 1 and in which Fig. 5 is aschematic diagram showing the control system utilized in the operationand control of the device.

Generally speaking the device shown in Figs. 1-4 inclusive constitutesan enclosing structure in which a perforated rotatable drum is mounted.This enclosing structure is provided at the top part thereof with aninlet adjacent which is disposed an air heating meansin the form of aplurality of gas jets. An outlet is provided near the bottom of theenclosure through which air is drawn and expelled to atmosphere by meansof a suction fan. The material to be rendered is loaded into theperforated drum manually and during the rendering operation the renderedliquid is extracted continuously by suitable pumping means whichcooperates with a receiver disposed at the bottom of the apparatus andinto which the rendered liquid is caused to flow by the action ofgravity. With reference to Fig. 1 the numeral 1 designates. a metallicchannel member which is disposed on the opposite side of the machinefrom a similarly constructed and arranged channel 2 as shown in Fig. 3.As can thus be seen in Fig. 3 the ends of channels 1 and 2 areinterconnected by a third channel designated by the numeral 3. Insimilar fashion the right hand end of the device as viewed in Fig. 1 isprovided with a channel similar to channel 3, this latter channelhowever is not apparent in any of the figures of the drawings. Thus itwill be understood that the machine rests on a framelike base made up ora rectangularly arranged channel structure which is mounted'on feet 4,5, 6 and 7. Afiixed as by welding or other suitable means to the cornersof the channel frame above described is a plurality of angle irons 8,. 9and 10, the angle iron disposed at the fourth corner not being visiblein any of the views of the drawings. A rectangular channel frame.similar to that constituting channels 1, 2 and 3 and the other channelnot shown is mounted atop the corner posts 8, 9 and 10 and the remainingpost which does not appear in the drawings.

receiver. In this way the flow of exhaust air is thorough- I ly andefficiently separated from the rendered liquid. According to anotherfeature of the invention a part of the wall of the machine is hingedlymounted so as to constitute an access door through which the solidresidue may be removed and which also closes oli the exhaust passage andthe receiver reservoir when the solid residue is being accompanyingdrawings in which Fig. 1 is a side view of a rendering machine embodyingthe invention: Fig. 2

This channel frame as best shown in Fig. 3 comprises a front channel 11,a back channel 12, and an end channel 13, the opposite end channel notappearing in any. of the views of the drawings. As already explained theframe of the machine can be assembled by welding or other suitabletechnique.

Affixed to the right hand end of the frame of the machine as viewed inFig. l is a pair of end plates designated in Fig. 2 by the numerals 14and 15. These end plates can be afiixed to the frame by suitable screwsor by welding or by other means. As is best shown in Fig. 4, the

left hand end of the machine as viewed in Fig. 1 is provided with a pairof end plates 16 and 17 which are aifixed to the frame in a mannersimilar to the manner employed in securing end panels 14 and 15 inposition. As is shown in Figs. 1 and 3, a'side panel 18 is constructedwith a vertical portion 19 and an integrally formed downwardly slantedportion 20. As is shown in Fig. 3 the opposite side of the machine isprovided with a side panel generally designated by the numeral 21 whichconstitutes a vertical portion 22 and an inclined portion 23.

As is best shown in Fig. 3 a pair of channels designated by the numerals24 and 25 are arranged in vertically spaced relation and are disposedhorizontally, these channels being affixed as by welding or otherwise tothe corner angles 8 and 9. Since the channels have their flanges turnedinwardly they are arranged to constitute mounting means for a pair ofaccess doors 26 and 27. These doors are respectively provided withhandles 28 3 and 29 and obviously'are slidable along the frame definedby the flanges of the channels 24 and 25.

As is seen in Fig. 3 the opposite side of the machine is 'similarlyprovided with access doors 30 and 31 which *are'mo'unted in 'the lowerhorizontally disposed channel interior of the enclosing'structure can behad from either side of the machine via the access doors 26 and 27 onone side or via doors 30 and 31 on the other side.

As is shown in Fig. 3 a pair of horizontally disposed channel membersisaffixed to the end channels as by welding and these horizontal channelsare designated by the numerals 35 and 36. A cover plate 37 isrectangular in shape andthe left hand edge thereof as viewed in Fig. 3is mounted on the channel 25 and the right hand edge thereof .issupported by the channel 35 by way of a mounting strip 38 atfixed tochannel 35 by bolts 39 and afiixed to cover plate 37 by bolts 40.Preferably the cover plate 37 is constructed of'a suitable heat insulat--'-ing material arranged in a frame of metal.

A suitable insulating material for this purpose is glass wool. Disposedopposite the cover plate 37 is a similar cover plate 41 the right handedge of which as viewed in Fig. 3 rests on the channel 33 and the lefthand edge of which is supported on channel 36 by way of the supportplate 42 afiixed to the cover plate 41 by bolts 43 and secured to thechannel 36 by bolts 44.

As viewed in Fig. 3 a portion of the enclosing structure constitutes anaccess door 45 which is hingedly mounted at 46. Door 45 is movable fromthe position shown in Fig. 3 toward the right to its normal position sothat its right hand surface engages the surface 23A of the downturnedportion 23 of side plate 21.

The structure described above and including the end plates 14, 15,16 and17, the'side plates 18 and 21, the doors 26, 27, 30 and 31, the 'coverplates 37 and 41, all constitute enclosing structure for the rotatabledrum designated in Fig. 3 by the numeral 47. Drum 47 is perforated asindicated for example by the openings 48 and is provided with aplurality of internal baffles 49 and an access door 50 which normally iscovered by a cover plate 51 secured to the drum by a plurality of bolts52. Drum 47 is rotatably mounted on shaft 53. Shaft 53 is supported ateach end on suitable cross pieces which are horizontally disposed andone of which is welded to the corner posts at the right hand end of themachine as viewed in Fig. l and the other of which will be described.-It will be understood that these cross pieces support end bearings onwhich the shaft 53 is rotatably mounted.

As is best shown in Fig. 3 the space between the horizontally disposedchannels 35 and 36 constitutes an inlet passage through which air flowsinto the cavity formed within the enclosing structure and in which thedrum 47 -is mounted. Furthermore as'shown in Fig. 3 the upwardlyinclined passage 54 communicates with a hori- "zon'tally disposedtransversely extending passage 55.

liquid from the sump 57. The receiver 56 and sump 57 normallyaccumulatethe rendered liquid due to the "fact that door 45 normally is disposedwith its right 4 hand surface in engagement with the surface 23A asviewed in Fig. 3 as alreadyexplained.

The left hand extremity of exhaust conduit 55 connects with a largevertically disposed exhaust conduit 58A in which a blower fan designatedin Fig. 4 by the numeral 59A is mounted. Blower fan 59A as best shown inFig. 4 is driven by a motor 60A which in turn is mounted on a table 61by bolts 62. The motor 60A is arranged so as to drive the fan 59A by abelt 63. It will be understood that the vertical conduit 58A is arrangedso as to extend upwardly and outside of the building in which themachine is mounted so as to exhaust the fumes resulting from therendering process to atmosphere.

For the purpose of applying heat to the air supplied through the inletpassage, a pair of horizontally disposed fuel gas conduits 64 and 65 aremounted adjacent the channels 35 and 36 respectively. These conduits areprovided with gas outlets 66 and 67 which constitute a plurality of gasjets disposed in the path of air following the direction of the arrowsas shown in Fig. 3. In this way heat is imparted to the incoming airwhen gas from the jets is ignited.

In order to insure that the incoming air will be efficiently heated, abafile plate 68 as shown in Fig. 3 is secured to "a pair of horizontallydisposed channels 69 and 70 which in turn rest on the end channels ofthe frame. It will be understood that the bafile plate 68 functions toprevent air from coming into the inlet passage from directly above thepassage and causes this air to follow the arrows and into closeproximity with the sources of heat.

Gas to theconduits 66 and 67 is supplied through a main conduit 71 bestshown in Figs. 1, 2, and 3. As is best shown in Fig. 1 horizontallydisposed conduits 72 and 73 lead from the main conduit 71. Conduit 72 isconnected with the vertical conduit 74 which in turn connects to a pairof vertically disposed conduits 75 and 76 as best shown in Fig. 4 whichin turn connect to the conduits 64 and 65. In similar fashion thehorizontally disposed conduit 73 connects to a vertically disposedconduit 77 which in turn connects with vertical conduits 78 and 79 asbest shown in Fig. 2 which in turn communicate respectively with theconduits 64 and 65. As is best shown in Fig. 2 a suitable conduit isprovided whereby gas is supplied to a pilot light and this pilot conduitis designated by the numeral 80.

The operation of the device as described thus far is as follows: Withburning gas issuing from gas outlets 66 and 67 and with the fan 59Aoperating, a current of air is drawn through the inlet between channels35 and 36 down through the drum 47 and out through the outlet passage54, 55 to atmosphere via conduit 58A. Meanwhile the drum 47 is rotatedby suitable means yet to be described and the rendered material disposedwithin the drum is agitated due to the rotation of the drum 47 and tothe action of baffles 49. The heated air passes through the material tobe rendered. The rendered liquid falls down into the receiver 56, 57 dueto the action of gravity, the solid residue being retained within thedrum 47. When a rendering operation is completed the 'machine is shutdown, the gas is shut 013, and the drum and 31. Bolts 52 and door 51 aremanually removed and the rendered solid material within the drum 47 isdumped out through the access opening 51 onto door 45 and panels 20 and23 by rotating the drum 47. During the rendering operation the pump 59continually draws oif rendered liquid.

In order to atford ready access to the end of the intc rior of theenclosing structure an access door 81 having a handle 82 may be suitablymounted in known fashion to the end plate 15 as best shown in Fig. 2. Itwill be understood that at least'a portion of the solid material dumpeddown on to the hingedly mounted plate 45 may shown in Fig. 4 the shaft53 of the drum 47 is mounted in a bearing 84 secured by bolts 85 to asupporting frame 86 secured by bolts 87 atop table 88. Aflixed to shaft53 is a sprocket 89 on which a driving chain 90 is mounted which in turnis driven by the sprocket 91. Sprocket 91 is mounted on shaft 92 whichin turn constitutes one ele- -ment of a speed changer designatedgenerally by the numeral 93 in the drawings. Also constituting one shaftof the speed changer 93 is shaft 94 and its associated pulley 95 onwhich a belt drive 96 is mounted and which in turn cooperates with thepulley 97 mounted on the shaft 98 of main motor 99. Motor 99 is affixedby bolts 100 to the table 83. Thus with power applied to main drivingmotor 99 the speed changer 93 is actuated through its shafts 94 and 92and in turn drives the chain 90 to impart rotary motion to sprocket 89and shaft 53.

For the purpose of controlling the motor 99 in such fashion as to impartcontrolled stopping movement thereto the arrangement shown in Fig. 5 hasproved to be satisfactory. For instance the access door 50 of drum 47should bear a predetermined space relationship to the access doors 26and 27 or 30 and 31 in order to perform a loading or unloadingoperation. For this reason suitable switch means dependent on theangular relationship of the drum 47 relative to the doors 30, 31 and 26,27 is used together with a suitable magnetic brake to determine theeXact position at which the drum stops when the machine is shut down.

As is shown in Fig. 5 thedriving motor 99 is designated by the letter Mand the drum 47' or load on the motor is designated by the letter L. Theshaft 53 is schematically represented in Fig. 5 as a dotted line. InFig. 5 the letter B designates the rotatable element of a magnetic brakewhich in actuality is formed integrally within the speed changer 93 andis not shown in detail in Fig. 4 since this particular device forms nopart of the present invention.

The cam operated switch designated by the letters CS is also aflixed tothe shaft 53 and is designated schematically in both Figs. 4 and 5.

Energy to the driving motor 99 is supplied through lines L1, L2 and L3by way of the contacts of the relay generally designated by the numeral101. The circuit for energizingathe coil 102 of relay 101 includes thestop-button 103 which of course is normally closed in conventionalfashion and the start button 104 which is normally open together withcertain elements of the selector switches S1 and S2.

In order to start the motor the selector switches S1 and S2 are bothclosed in their down positions, that is, with their blades connectedwith their lowermost poles. With the switches S1 and S2 down, the startbutton is depressed. In this manner a circuit is completed from L2through the stop button 103, start button 104, conduit 105, switch S1,cross conduit 106, conductor 107, switch S2, conductor 108, conductor109, coil 102 of relay 101 and back to line L1. When so energized theoperating elements of relay 101 pick up and close. all of the relaycontacts. t

Should the operator not close either or both of the switches S1 or S2 totheir down positions, i .e. should both switches be open as shown inFig. 5, the system will still start the motor 99 because the switch S1and conductor 106 are by-passed by the normally closed contacts of relay125 which are connected between line and line 107 via 1ine126 andbecause the switch S2 and conductor 108 are by-passed by the normallyclosed contacts of relay 127 which interconnect with lines 107 and 109via the lines 129 and 128 respectively. i

When the coil 102 of relay 101 picks up, power is supplied to motor Mand the motor starts. The relay coil 102 is sealed in in conventionalfashion by a circuit comprising conductor 110, the upper connectingelement 111- of the relay, and conductor 112 which circuit constitutes ashort circuit around the start button. Thereafter release of the startbutton does not result in a dropping out of the relay 101. When relay101 picks up the coil 113 of relay 114 is energized and picks up itsnormally closed contacts thereby de-energizing the field coils 115 ofthe magnetic brake. As is shown in Fig. 5 the field coils 115 of themagnetic brake are energized from a'suitable source of alternatingcurrent and a conventional rectifier 116 which is arranged in series'With a rheostat 117 and with the contacts of the relay 114. In thismanner the magnetic brake is de-energized as the motor simultaneouslybegins to drive the drum 47.

In practice I have found that it is desirable to control a renderingoperation on a definite time basis. Thus after the timer indicates thecompletion of an operation, one of the switches S1 or S2 is moved fromits intermediate or down position to its up position, the particularswitch depending on whether it is desired to stop the drum 47 with itsaccess opening 50 adjacent to doors 26, 27 or whether it is desired tohave the access door 50 stop adjacent to doors 30 and 31. In any eventone of the selector switches S1 or S2 is moved to its up position.Assuming that the switch S1 is moved to the up position the coil of timedelayed relay is energized and its contacts opened after a predeterminedinterval of delay and the circuit from line L2 energizing the relay coil102 includes the stop button 103, the connector 110, the contact 111,the connector 112, connector 105, the switch S1, the conductors 119 and120, the normally closed contact 118 of the cam switch CS, the conductor107, the switch S2, the conductor 108 (or the lines 129 and 128 andcontacts of relay 127 if S2 is in its intermediate position) andconductor 109 through the coil 102 and back to line L1. Thus on the nextsucceeding revolution of drum 47 and shaft 53 occurring after timedelayed operation of relay 125 the cam portion 121A of the cam switch CSwill open the cam switch 118 at a predetermined time relative to theposition of the drum 47 with respect to one or the other of the accessdoors 26, 27 or 30, 31. In this manner the relay coil 102 is deenergizedand the coil 113 of relay 114 is deenergized and closes its contactsthereby to apply power to the magnetic coils 115 of the magnetic brakeB. With the brake applied and the power off of the motor 99 the drum 47is stopped in a predetermined fashion at a predetermined time.

In similar fashion it will be understood that the drum 47 could bestopped at a different position relative to the enclosing structure andto the doors by simply closing the selector switch S2 to the up positionwhile leaving the selector switch S1 in its down or intermediateposition.

'In this manner control would be placed on the cam switch contact 122which through conductors 123 and 124 and other circuit elements woulddeenergize the coil 102 after predetermined time delay caused by delayedoperation of time delay'relay 127 Whose contacts are in parallel withcontacts 122 when switch S2 is in its up position, in a manner which isobvious from Fig. 5.

In Fig. 4 the cam switches 118 and 122 are'schematically designated andthe cam portion 121A of the ca 121 is indicated schematically.

From the description thus far it will be seen that if it is desired tostop the drum 47 with its access door 51 adjacent the one set of doorssuch as 26, 27 for example, one selector switch such as S1 would beclosed to its up position and the drum would promptly stop rotating andthe access door 51 would register with the doors 26, 27.

, Thereafter bolts 52 and door 51 are removed by an operator who gainsaccess thereto via doors 26, 27. Thereafter the switch S1 is pulled toits intermediate or down position and the start button 104 depressed.The drum 4'] beginsto rotate again and the solid' residue is thrown outthrough door-51 and into thecavity of the machine, the solids fallingdown onto panels 20, 23 and door 45. When the solids are all removedfrom drum 47 switch -S1 or $2 is moved to its up position and the drum47 stops with its door 51 in registry with cavity doors 26, 27 or 30, 31as the case may be. The machine is then ready to be reloaded manually.

After reloading door 51 is afiixed in place by bolts 52 and door 45 isswung clockwise to engage panel 23 at 23A and the start button 104depressed to begin another rendering cycle.

While I have shown and described a particular embodiment of theinvention I do not wish to be limited thereto and intend in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity and indirect communication therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the-lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, means for causing atmospheric air to enter saidcavity through said inlet and to leave said cavity through said outlet,means defining a plurality of fuel gas outlets disposed about theexterior of said inlet passage and adjacent thereto, and bafile meansspaced from the outer part of said inlet passage for causing airentering said inlet passage to pass closely adjacent said gas outletsand to follow a tortuous path to the interior of said cavity whereby theair is heated without exposing the material in said rendering cavity tothe flames formed at said gas outlets.

2. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity and indirect communication therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, means for causing atmospheric air to enter saidcavity through said inlet and to leave said cavity through said outlet,a pair of spaced substantially parallel fuel gas conduits disposedrespectively on opposite sides of said inlet passage, a plurality of gasoutlets formed in each of said conduits, and bafile means spaced fromthe outer part of said inlet passage for causing air entering said inletpassage to pass closely adjacent said gas outlets and to follow atortuous path to the interior of said cavity whereby air flowingtherethrough is heated without exposing the material to be rendered insaid rendering cavity to flames formed at said gas outlets.

3. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity andindirect communication therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, a portion of said structure generally opposite fromsaid outlet being movable from a normal position to another position toestablish an access opening to the bottom of said cavity, means forcausing atmospheric air to enter said cavity through said inlet and toleave said.

cavity through said outlet, means defining a plurality of fuel gasoutlets disposed about the exterior of said inlet passage and adjacentthereto, and baffle means spaced from the outer part of said inletpassage for causing air entering said' inlet passage to pass closelyadjacent said gas outlets and to follow a tortuous path to the interiorof said cavity so as to prevent exposure of the contents of saidrendering cavity to contact with flames at said gas outlets.

4. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity and indirect communication therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, a portion of said structure generally opposite fromsaid outlet being movable from a normal position to another positionpreventing communication between said cavity and said receiver, meansnormally causing atmospheric air to enter said cavity throughsaid inletand to leave said cavity through said outlet, and means disposedadjacent said inlet for increasing the temperature of air entering saidcavity through said inlet.

5. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed. below said cavity andin direct communication therewith, an inlet passage formedin the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, a portion of said structure generally opposite fromsaid outlet being hingedly mounted for swinging movement from a normalposition to another position to establish an access opening to thebottom of said cavity and to prevent communication between said cavityand said receiver, means normally causing atmospheric air to enter saidcavity through said inlet and to leave said cavity through said outlet,and means disposed adjacent said inlet for increasing the temperature ofair entering said cavity through said inlet.

6. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity and indirect communi cation therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, a portion of said structure generally opposite fromsaid outlet being movable from a normal position to another position toestablish an access opening to the bottom of said cavity and to preventcommunication between said cavity and said outlet, means normallycausing atmospheric air to enter said cavity through said inlet and toleave said cavity through said outlet, and means disposed adjacent saidinlet for increasing the temperature of air entering said cavity throughsaid inlet.

7. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity and indirect communication therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, a portion of said structure generally opposite fromsaid outlet being movable from a normal position to another position toestablish an access opening to the bottom of said cavity, and to preventcommunication between said cavity and said outlet and between saidcavity and said receiver, means normally causing atmospheric air toenter said cavity through said inlet and to leave said cavity throughsaid outlet, and means disposed adjacent said inlet for increasing thetemperature of air entering said cavity through said inlet.

8. A rendering machine comprising enclosing structure defining therein arendering cavity and a liquid receiver disposed below said cavity and indirect communication therewith, an inlet passage formed in the upperportion of said structure and establishing communication betweenatmosphere and said cavity, an outlet formed in the lower portion ofsaid structure and establishing communication between atmosphere andsaid cavity, said outlet being disposed at a level below said cavity andabove said receiver, a portion of said structure generally opposite fromsaid outlet being hingedly mounted for swinging movement from a normalposition to another position to establish an access opening to thebottom of said cavity and to prevent communication between said cavityand said receiver, means normally causing atmospheric air to enter saidcavity through said inlet and to leave said cavity through said outlet,an upwardly slanted outlet passage leading from said outlet, and meansdisposed adjacent said inlet for increasing the temperature of airentering said cavity through said inlet.

References Cited in the file of this patent UNITED STATES PATENTS

1. A RENDERING MACHINE COMPRISING ENCLOSING STRUCTURE DEFINING THEREIN ARENDERING CAVITY AND A LIQUID RECEIVER DISPOSED BELOW SAID CAVITY AND INDIRECT COMMUNICATION THEREWITH, AN INLET PASSAGE FORMED IN THE UPPERPORTION OF SAID STRUCTURE AND ESTABLISHING COMMUNICATION BETWEENATMOSPHERE AND SAID CAVITY, AN OUTLET FORMED IN THE LOWER PORTION OFSAID STRUCTURE AND ESTABLISHING COMMUNICATION BETWEEN ATMOSPHERE ANDSAID CAVITY, SAID OUTLET BEING DISPOSED AT A LEVEL BELOW SAID CAVITY ANDABOVE SAID RECEIVER, MEANS FOR CAUSING ATMOSPHERE AIR TO ENTER SAIDCAVITY THROUGH SAID INLET AND TO LEAVE SAID CAVITY THROUGH SAID OUTLET,MEANS DEFINING A PLURALITY OF FUEL GAS OUTLETS DISPOSED ABOUT THEEXTERIOR OF SAID INLET PASSAGE AND ADJACENT THERETO, AND BAFFLE MEANSSPACED FROM THE OUTER PART OF SAID INLET PASSAGE FOR CAUSING AIRENTERING SAID INLET PASSAGE TO PASS CLOSELY ADJACENT SAID GAS OUTLETSAND TO FOLLOW A TORTUOUS PATH TO THE INTERIOR OF SAID CAVITY WHEREBY THEAIR IS HEATED WITHOUT EXPOSING THE MATERIAL IN SAID RENDERING CAVITY TOTHE FLAMES FORMED AT SAID GAS OUTLET.